This invention relates to apparatus and methods for processing a gaseous fluid while it is combined with a liquid in a transient foam. Processes that can be practiced on the foamed fluids include compression, expansion and condensation of the gaseous fluid; and heat exchange and chemical reaction with the gaseous fluid.
The foam state provides an enormous surface-to-volume ratio between the gaseous fluid and the liquid. Further, the liquid has a relatively large heat capacity. These properties of the foamed fluids result in almost instantaneous heat exchange between the gaseous fluid and the foamed liquid, and make possible the essentially isothermal compression and expansion of the gaseous fluid. Further, the foam has many times the density of the gaseous fluid alone, and hence can be processed with rotating equipment having a corresponding reduction in size, speed and cost as compared to equipment for processing the gas by itself.
A principle application of the invention relates to the control of the temperature of a gaseous fluid during compression and during expansion. More particularly, this aspect of the invention provides essentially isothermal compression and isothermal expansion of a gaseous fluid. To these ends, the invention teaches that a gaseous fluid be compressed, and conversely expanded, while it is foamed with a liquid. Heat rapidly transfers between the gaseous fluid and the foamed liquid during either process so that the gas experiences essentially no temperature change. Hence, both operations can be essentially isothermal.
More generally, the liquid foam can limit the temperature change of the gaseous fluid during compression and during expansion to any desired degree between the temperatures resulting from an isothermal process to a normal adiabatic process. Further, foam of initially supercooled liquid can chill the gas sufficiently to offset heat of compression so that after compression the gas is cooler than prior to contact with the liquid. Thus, this aspect of the invention in its broad scope relates to controlling the temperature of a gaseous fluid during compression and during expansion by containing the fluid in a liquid foam. However, for clarity of description this aspect of the invention is described principally with specific application to providing substantially isothermal processes.